1. Field of the Invention
The present invention relates generally to a speaker apparatus and, more particularly, to a speaker apparatus wherein a periphery of a diaphragm is supported by a frame.
2. Description of the Related Art
A dome-speaker shown in FIGS. 7A,7B is conventionally suggested as an example of the above speaker apparatus. FIG. 7A is an exploded half-sectional view showing a prior art dome-speaker. FIG. 7B is a half-sectional view showing the prior art dome-speaker of FIG. 7A.
In this dome-speaker, a circular pole plate 10, a magnet 11, and a yoke 12 constitute a magnetic circuit having a ring-like magnetic gap 13. The magnetic gap 13 is formed between a side surface of the pole plate 10 and an inner surface of the yoke 12. A frame 14 of resin is formed around the yoke 12. The magnetic circuit and the frame constitute an frame assembly.
A diaphragm 15 is arranged over the frame assembly. The diaphragm 15 is in a circular or elliptic shape. The diaphragm 15 has a vibrating portion 16 having a dome shape, a recess (or a groove) 17 provided along the peripheral edge of the vibrating portion 16, an edge damper 18a provided along the peripheral edge of the recess 17, and an edge damper frame 18b provided along the peripheral edge of the edge damper 18a. The edge damper frame 18b is provided along a horizontal support plane 14b of the frame 14.
The diaphragm 15 is provided with a rising portion 18c which vertically stands from the peripheral edge of the edge damper frame 18b. The rising portion 18c is provided along an inside surface 14a-1 of a projecting portion 14a formed outside the horizontal support plane 14b of the frame 14. The diaphragm 15 is provided with an engaging portion 18d formed from the top of the rising portion 18c. The engaging portion 18d is a plane parallel to a radial direction of the diaphragm 15. The engaging portion 18d engages an inside surface 14a-2 of the projecting portion 14a. 
The edge damper 18a, the edge damper frame 18b, the rising portion 18c and the engaging portion 18d constitute an edge portion 18. The vibrating portion 16, the recess 17 and the edge portion 18 are integrally formed of a single resin film and constitute the diaphragm 15.
The diaphragm 15 is arranged such that the rising portion 18c abuts the inside surface 14a-1 of the projecting portion 14a of the frame 14. The diaphragm 15 is attached to the frame assembly such that the center of the diaphragm 15 aligns with the center of the frame assembly. Positioning of the diaphragm 15 in a radial direction thereof with respect to the frame 14 can be done by the rising portion 18c. 
When the above edge damper frame 18b is arranged on the horizontal support plane 14b provided of the frame 14, the recess 17 is arranged in the magnetic gap 13. Positioning of the diaphragm 15 in an axial direction thereof with respect to the frame 14 can be done by the edge damper frame 18b. 
As above, the recess 17 can be properly arranged in the magnetic gap 13 of the magnetic circuit. A voice coil 19, which is formed by winding an electric wire, is adhered to the recess 17. The voice coil 19 is elastically supported by the edge damper 18a in the magnetic gap 13 along with the recess 17.
In the above speaker apparatus, the diaphragm 15 is attached to the frame 14 by adhering the edge damper frame 18b of the diaphragm 15 to the horizontal support plane 14b of the frame 14 with an adhesive. A frame cover 20 to protect the diaphragm 15 is provided over the diaphragm 15.
Generally, a speaker apparatus with a larger vibration area can generate a lager sound volume at a low frequency band (i.e. the lower register) due to a larger mass of the diaphragm and accordingly due to a lower minimum resonance frequency. And also, a speaker apparatus with a larger vibration area can generate a lager sound volume at a low frequency band due to a higher radiation impedance and due to a higher-sensitivity sound pressure characteristic.
With respect to the above prior art dome-speaker, however, the diaphragm 15 is attached to the frame 14 by adhering the edge damper frame 18b of the diaphragm 15 to the horizontal support plane 14b of the frame 14 with an adhesive. An adherence area needs to be larger for enhancing the strength of adherence.
That is, the width of the horizontal support plane 14b and that of the edge damper frame 18b need to be large for obtaining a sufficient adherence strength. In this case, the diameter of the vibrating portion 16 and that of the edge damper 18a become small. That is, the vibration area becomes small.